Activation Of Peroxymonosulfate By La-Sr-Co-Mn Perovskite For Degradation Of Tetrabromobisphenol A

In recent years,pollution of bromine-based flame retardants such as tetrabromobisphenol A to the surface and groundwater has occurred frequently.Because of its stable chemical properties,long-lasting pollution and high biological toxicity,it seriously threatens ecosystems,and there is an urgent need to develop efficient technologies to remove water pollution.In this study,B-site Co and Mn doping modification of lanthanide perovskite was used to prepare perovskite-type La0.5Sr0.5Cox Mn1-xO3-?(x=0,0.2,0.3,0.4,0.5,0,6,0.7,0.8 and 1)materials,and use this material to catalytically activate persulfate(PMS)to degrade TBBPA pollutants.In this paper,the relationship between the optimal substitution type and content of the B-site element of the LSCM material and the degradation reaction rate constant and its catalytic degradation efficiency are investigated.The source of the catalytic activity of the material and its degradation reaction mechanism are analyzed.The main content and results of the research are as follows:(1)In the characterization and comparison study of the catalyst,the order of low to high catalytic activity of the LSCM series materials with a calcination temperature of 950? was determined:LSM-950,LSCM 37-950,LSCM 28-950,LSCM 46-950,LSCM 55-950,LSCM 64-950,LSCM 73-950,LSC-950 and LSCM 82-950,the maximum reaction rate constant is LSCM82-950(k=0.171 min-1).The valence state of the active composition of the LSCM catalyst mainly depends on the calcination temperature.As the calcination temperature increases,the cation at the B position undergoes thermal reduction.The redox effect on Co3+/Co2+?(Mn4++Mn3+)/Mn2+makes the LSCM82 catalyst have good catalytic activity.(2)Evaluation and analysis of the diffusion rate of interstitial oxygen and oxygen ions before and after the use of LSCM catalyst shows that the presence of oxygen vacancies on the surface or sub-surface layer of LSCM material is conducive to the adjustment of the valence state by redox of valence ion,and the increase of oxygen vacancies can promote LSCM catalysis activity.In addition,an appropriate amount of interstitial oxygen can promote the electron transfer rate of the LSCM material and improve its catalytic activity,while excessive interstitial oxygen will hinder the process.(3)Research on the repeated use of the catalyst shows that the relative acidity of the LSCM82 material is basically stable and can be reused four times.Humic acid HA will cover the active sites and intermediate products of the catalyst,weakening the degradation rate of the target pollutants,Cl-will be oxidized by PMS to produce strong oxidizing HClO/Cl2,which is conducive to increase the degradation rate.The application of LSCM82-950/PMS under the condition of neutral pH can not only make the catalyst cobalt leaching very small,but also achieve the maximum TBBPA degradation effect.